Saw Mill River

Not to be confused with Sawmill Brook (New Jersey).

Template:Geobox The Saw Mill River is a 23.5-mile (37.8 km) tributary of the Hudson River in Westchester County, New York, United States. Rising from an unnamed pond north of Chappaqua, it flows to Getty Square in Yonkers, where it empties into the Hudson as that river's southernmost tributary, and it is the only major stream in southern Westchester County to drain into the Hudson instead of Long Island Sound. It drains an area of 26.5 square miles (69 km²), most of it heavily developed suburbia. For 16 miles (26 km), it flows parallel to the Saw Mill River Parkway, a commuter artery, an association that has been said to give the river an "identity crisis."

Industry in Yonkers developed along the Saw Mill, so polluting the river by the end of the 19th century that a local poet called it a "snake-like yellow scrawl of scum". Today, the U.S. Environmental Protection Agency (EPA) rates the river's last 2.9 miles (4.7 km) as an impaired water body.

In the 1920s, the last half-mile (800 m) of the stream was routed into tunnels and culverts under downtown Yonkers, a process partially reversed in the early 21st century when it became the first major New York waterway to be daylighted.

Course

Headwaters of the Saw Mill in the woods of Chappaqua, just below its source

The river rises from a 1.75-acre (7,100 m²) pond in a wooded area of the town of New Castle roughly 2 miles (3.2 km) north of Chappaqua, a half-mile (800 m) west of Quaker Road State Route 120 (NY 120) and just south of Stony Hollow Road, at an elevation of 490 feet (150 m) above sea level. It wends and meanders past a cemetery, between hills, through a residential area of houses on large wooded lots in a generally southward direction. Just north of Marcourt Drive, its first crossing, it is impounded to create another small pond. In this area it is frequently channelized and impounded as part of the landscaping on the area's large residential land lots. After crossing under Kipp Street, it bends eastward to cross under Quaker Road.

A short channelized portion runs through the front yard of a large house on Quaker southeast of the intersection, after which the river flows back under Quaker and behind the houses on the west side into another impoundment, Chappaqua's Duck Pond. From its outlet it continues southeast between Quaker on its east and Douglas and Mill River roads on the west to the Saw Mill River Parkway. Just west of the Chappaqua train station, it turns southwest to parallel both the parkway and Metro-North Railroad's Harlem Line as both cross into the town of Mount Pleasant. At this point the river is at 340 feet (100 m) in elevation, a loss of 150 feet (46 m) from its source. Just south of the town line, it receives Tertia Brook, its first named tributary, from the east.

Chappaqua Duck Pond

A mile past the town line, the river and its eponymous parkway pass the village of Pleasantville to the east. There the river crosses under the parkway to flow on its west, then crosses and recrosses at the Pleasantville Road (State Route 117) exit. Both make a long turn to the southeast and then back to the southwest around Graham Hills County Park, where it receives Nanny Hagen Brook from the east, before crossing back to the parkway's west in the flood plain around the base of the hills as road, river and rail pass the unincorporated hamlets of Thornwood, and Hawthorne, where the Harlem Line turns to the south.

Just east of the Taconic State Parkway, the river again crosses under the Saw Mill Parkway, then the Taconic. Shortly after that exit it crosses under Saw Mill River Road (State Routes 9A and 100) and some of the ramps to them from the interchange, then under the Saw Mill Parkway. Both turn south again, then southeast, following the eastern edge of the Pocantico Hills, joined on the west by the North County Trailway bike path, on the right-of-way of the former New York and Putnam Railroad, known as the "Old Put".

The river crosses under the parkway again to form the eastern edge of a plant nursery on Saw Mill River Road, then recrosses as the river, bike path, parkway and Saw Mill River Road all bend around the northwest corner of Eastview, where the Saw Mill drops below 200 feet (61 m) in elevation, a loss of 100 feet (30 m) since Chappaqua. A turn back to the southwest around Tarrytown Lakes County Park puts the river at the outskirts of Elmsford. There it receives Mine Brook from the east.

Woodlands Lake in Greenburgh

Here the bike path ends amidst the dense urban development, but the parkway continues, and the two again draw close as they enter the town of Greenburgh and intersect the Cross Westchester Expressway (Interstate 287). A new bike path, the South County Trailway, begins here just south of the West Main Street (State Route 119) bridge north of the Rum Brook confluence. Past that the parkway, trailway and river all turn southwest, where they intersect the New York State Thruway) (Interstate 87) at an oblique angle. For the next mile the Thruway remains close to the river, and Saw Mill River Road, now just carrying NY 9A, returns to the corridor just east of the Thruway as well.

This leads to V. Everit Macy Park on the west. As part of the park facilities, the Saw Mill River is impounded into Woodlands Lake, the largest impoundment on the river, used as a water supply by the local communities of Ardsley and Dobbs Ferry, whose northern village line is just to the south. The river runs close to the boundary between the two, as the Thruway gradually veers away to the southeast just past the Ashford Avenue bridge.

Newly daylighted Saw Mill River in Van Der Donck Park, Yonkers

Continuing south-southwest, the river along with the parkway and trailway enter Hastings-on-Hudson, its greenbelt the only major break in the village's dense suburban development. It slowly veers toward a more southerly heading, and enters the Nepera Park neighborhood of Yonkers after one mile (1.6 km), just south of Farragut Parkway. Once in the neighborhood, the river flows through a Yonkers sewage treatment plant, the other impoundment of the river. After leaving the plant, 1.5 miles (2 km) to the south of where the river entered Yonkers, the parkway and trailway diverge from the river after 16 miles (26 km), to climb over the watershed divide to Tibbetts Brook. Saw Mill River Road continues to parallel its namesake.

Bending to the southwest again, the Saw Mill flows in a narrow channel through an industrial and commercial area. A mile south of the parkway, it flows through the middle of the former Smith Carpet Mills site, where it finally drops to 100 feet (30 m) in elevation. After crossing Ashburton Avenue, the river bends around to flow briefly to the northwest under Nepperhan Avenue after crossing the Old Croton Aqueduct. It circles around War Memorial Field, giving up its remaining elevation as the Hudson River nears.

The river turns south again past the park. After passing the towers of a large housing project to its west, it is routed into an underground tunnel at Chicken Island, the triangle between Nepperhan and Palisade avenues and School Street. At Van der Donck Park in downtown Yonkers, it resurfaces as it flows past the post office. For its final hundred feet (30 m), it re-enters a tunnel under the train station and the tracks of the Hudson Line, after which culverts empty it into the Hudson south of Dock Street.

Watershed

The Saw Mill's 26.5-square-mile (69 km²) watershed is limited by the hilly topography of central Westchester County to a valley that averages 1.4 miles (2.3 km) wide; the only wider spots are the Mine Brook and Tarrytown Lakes subwatersheds and the river's mouth in downtown Yonkers. The highest elevation in the watershed is 710 feet (220 m), reached in two locations: the summit of Sarles Hill north of Pleasantville, and an unnamed height of land about 1,200 feet (370 m) southwest of Buttermilk Hill, west of Hawthorne.

In terms of administrative jurisdiction (from source to mouth), 10% of the watershed is in New Castle, 42% in the town of Mount Pleasant, 33% in Greenburgh, and 14% in Yonkers. In terms of land use, 63% of the watershed consists of dense urban or less dense suburban development, 34% forest, and 1% agricultural. The woodlands buffering the river and the South County Trailway is one of the few significant areas of open space in the county south of I-287.

Some 110,000 people live in the watershed, in communities varying from small villages to Yonkers, New York's fourth-largest city. This is 12% of the county's total, on 6% of its area. The watershed's population density varies from 1,000 per square mile around the headwaters at Chappaqua to 10,000 around the mouth. It averages to 4,151 per square mile, twice that of the county and ten times the density for the state.

On the north, the Saw Mill watershed is bordered by the watersheds of Gedney Brook and the Kisco River, both of which drain into New Croton Reservoir on the Croton River, one of several large reservoirs in that watershed that are part of New York City's water supply system. On the northeast, the adjacent watersheds drain into Kensico Reservoir, another that supplies the city. Moving south, the next watersheds are tributaries of the Bronx River, then Yonkers' Grassy Sprain Reservoir and finally Tibbetts Brook. To its west in the narrow strip between the Saw Mill and the Hudson are the Pocantico River and Sheldon Brook watersheds at the north end of the watershed, and those of unnamed shorter streams at the south.

History

Pre-colonial

The Saw Mill River, then known as the Nepperhan River, acted as a boundary between the Manhattan Indians and the Weckquaesgeeks, members of the Algonquian family who fished the region's streams and lakes with rods and nets. The Manhattans occupied present-day New York City north to the river, while the Weckquaesgeeks occupied the land from the river north to the Pocantico River. The Manhattans' principal village, Nepperamack, was on the site of present-day Yonkers where the Saw Mill River discharges into the Hudson River. The Weckquaesgeeks settled the site of today's Dobbs Ferry, and on the river's banks west of White Plains.

Colonial period

Philipse Manor Hall, a National Historic Landmark. Not pictured is the daylighted Saw Mill River that once again flows nearby.

In 1639, the Dutch West India Company acquired from the Manhattans the area that would become Yonkers. Seven years later, Dutch settler Adriaen van der Donck was granted part of this land, including the southern section of the Nepperhan Creek. His estate was called Colen-Donck, for "Donck's colony", and the Nepperhan became known as Colen-Donck's Kill, after the Dutch word for "stream". He built a sawmill and a gristmill on his land. After his death, his widow sold off the land in several sales.

In the 1670s, part of Donck's land passed to Frederick Philipse, who was rewarded with 90,000 acres (360 km²), including the lower river, for declaring his loyalty to the new British rulers of New Netherlands. Philipse and his descendants, part of a pro-British political faction in the New York Colonial Assembly, named their manor Philipsborough and ran it as a quasi-feudal farm, hiring tenants to work the land. When Frederick Philipse III took over the farm, he moved from his townhouse in New York City to Philipse Manor Hall, a riverside mansion. During the American Revolution, Patriots forced him to flee to British-occupied New York City and later to Great Britain. After the war, his land was confiscated and sold to his tenants.

Commercially navigable only at its mouth, the river was useless as a way to bring crops to market, limiting settlement further upriver. Nevertheless, the roots of some present-day communities along the river were established during the 18th century. By 1704, the area that is today Elmsford was known as Storm's Bridge, after Abraham Storm, who established a tavern at the junction of the Saw Mill River and Tarrytown roads (today routes 9A and 119) that is the center of that village today.

From a different direction, European settlers came to the river's headwaters. Quakers had been coming to Long Island since the previous century to escape religious persecution in England; their descendants began moving across the Sound to southeastern Westchester, establishing Mamaroneck and Purchase in the 1720s. Their northern expansion continued in the following decade; another community established itself at "Shapequaw", north of the present hamlet of Chappaqua. One early settler, John Reynolds, established a 100-acre (40 ha) farm between what is today Roaring Brook Road and Kipp Street along what is still called Quaker Road (Route 120). In the middle of the century, the community built its meeting house; it and other buildings of the era are today part of the Old Chappaqua Historic District, listed on the National Register of Historic Places in 1974.

Both communities played minor parts in the Revolutionary War during the 1770s. The pacifist Quakers opened their meetinghouse as a hospital for injured Continental Army soldiers. Storm's tavern was a gathering place for Continental officers and, later, their French colleagues. George Washington is said to have referred to the "ford over the Nepperhan at the elm tree", referring to a wide tree no longer extant; a century later the residents used that remark as the basis for the name of their then-hamlet.

Never of strategic importance, the river's settlements and accompanying roads did see skirmishes. After the Battle of White Plains in October 1776, the Continental Army retreated to the vicinity of Peekskill while the British withdrew to Kingsbridge in what is now the Bronx, leaving most of Westchester unoccupied neutral ground. However, it was not demilitarized. Local militias and raiding parties affiliated with both sides terrorized sympathizers and supporters of the other side, as well as each other.

In November 1777, three young men with Patriot sympathies walking along the Dobbs Ferry Road, now Ashford Avenue, near the river crossing came upon a group of horsemen affiliated with Kipp's Regiment, one of the most feared of the Loyalist militias in the county. The young men taunted their rivals, who then beat them so severely that two later died. The survivor was awarded a pension, believed to be the first in U.S. history, by the Continental Congress.

Later that month, at Elmsford, Emmerich's Chasseurs, an elite unit of Loyalist militia and Hessian mercenaries staged a midnight raid on Storm's Bridge. They were hoping to capture Storm and his cousins the Van Tassels, all active in the local Patriot militia. Storm himself was not present, so after burning and looting his house and tavern the raiders went to the Van Tassel houses and did the same. At one they had Cornelius Van Tassel Jr., one of the cousin's teenage son, trapped. He hid on the roof while the house around went up in flames, then jumped off, fended off some putative captors, then jumped into the nearby Saw Mill to escape. He got away, but died soon afterwards from hypothermia brought on by the river's cold water.

The river and its adjacent terrain also conferred some tactical advantages to those who knew it. One skirmish began when a Patriot militiaman, Jake Acker, was hunting in a bushy area of the Saw Mill's flood plain on its eastern bank at Elmsford when he saw a large group of British soldiers and Loyalist supporters passing on the road to Storm's tavern. Acker, who had a reputation for marksmaship, began sniping at them. From his concealment he shot and fatally wounded one. Having created a distraction, he changed his position, reloaded his musket and killed another. Hearing the shots, other local Patriots came to Acker's aid, and eventually all but one of the larger force were killed or captured.

Some of the Continental Army's leaders spent time in the Saw Mill valley during the war. Polish general Thaddeus Kosciusko was headquartered for a time during 1778 at the farmhouse of Patriot Joseph Young, located at the junction of Saw Mill River Road and the upper road between Tarrytown and White Plains along what was then the town line between Greenburgh and Mount Pleasant (today State Route 100C, in Eastview)), an intersection known then as Four Corners. That summer, General Horatio Gates and his former aide Colonel James Wilkinson fought a brief, inconclusive duel, part of their long-running feud, at a nearby blacksmith's shop.

Later in the war, Young's farmhouse and Four Corners were the site of its largest military engagement near the river. By 1780, the Continentals were operating much more freely around northern Westchester. But they had to stay on the move in case the British and their Loyalist allies launched an attack. In January of that year, one company of approximately 250 troops from Massachusetts lingered long enough at Four Corners for local Loyalists to inform the British, who raised a force of approximately 100 cavalry and 400–500 infantry at Fort Washington, today on the northern tip of Manhattan, who marched from there to Yonkers and up the Saw Mill in a single February day, arriving at Four Corners that night. The Continentals put up stiff resistance, aided by the darkness, heavy snow cover and fatigue of their opponents. Ultimately, however, they were overwhelmed and outnumbered, and most were killed or taken prisoner. The British and their Loyalist and Hessian allies celebrated the victory by burning down the Young house.

1800s and 1900s

After the confiscation of the Philipse property, the town of Yonkers was established in 1788. Most of the town's economy in the early 19th century was derived from the river. As of 1813, there was a small wharf slightly upstream from the mouth where the sloops that carried river trade put in. Five small mills existed along the river above the village, all with their own dams, small mill ponds, and nearby tenements for the workers. The stagecoach route up the Post Road stopped at an inn near the bridge; a few stores existed to supply the workers there and at the mills. Some pastures and orchards existed, but the rocky soil deterred most attempts at farming. (A historian later wrote that it was said at the time that "the succession of boulders was so continuous that one might have stepped from Getty Square to the present Glenwood without setting his foot upon the ground".) Between the rocky soil and Wells' general refusal to sell or lease most of his land, there were so few settlers in Yonkers that two schoolhouses built during the Revolution fell into severe neglect due to the lack of students.

The manor house and the land around it at the river's mouth that is today downtown passed through several owners until 1813, when New York merchant Lemuel Wells bought the 320 acres (130 ha) around the manor house. Wells neither subdivided nor developed the property, although he did extensively landscape the manor house grounds. In 1831, Wells built a long wharf into the Hudson just above the mouth of the Saw Mill for the steamboat service which had been established between New York and Albany. Otherwise, the property remained largely unchanged until his death in 1842.

Map of Yonkers in 1813, at the time of Wells' purchase of the area

Maps of the property from the time of Wells' purchase and his death show the Saw Mill's mouth widening into a small estuary before reaching the Hudson. The south bank of the river at the mouth had a 40-foot-high (12 m) bluff. The only construction directly affecting the river was the bridge that carried the Albany Post Road, today Riverdale and Warburton avenues, part of U.S. Route 9 and Route 9A, over the river.

Wells had survived the death of his first wife and all four of his brothers; he also had no children, leaving him without a clear heir. His estate was further complicated by his lack of a will. Accordingly, under New York law at the time, his holdings were divided among his widow, fifteen nephews and one grand nephew. They decided to subdivide and sell the property, and within a few years more buildings had gone up, just in time for the construction of the Hudson River Railroad in 1848, which laid its track on a causeway right across the river's mouth. Over the next several decades, as Yonkers' population grew rapidly, leading it to incorporate as a village and then, in 1872, a city, the rest of the estuary was filled in and narrowed and the bluffs on its south side graded out of existence.

By the later decades of the 19th century, industry had grown up along the river's lower portion. So much pollution was dumped into the river from the factories alongside it that a local poet lamented the Saw Mill's decline in an 1891 quatrain:

'Tis now, at Yonkers's spreading feet,
A flow with odorous sins replete;
Its nitid bosom has become
A snake-like yellow scrawl of scum.

To let the river replenish itself, most of the dams that had been built were removed in 1893. Ten years later it had somewhat recovered, and people were again using it for drinking water and swimming.

In the late 19th century, the New York and Putnam Railroad was built along the river from Putnam County to central Yonkers, and thence to Tibbets Creek and the Harlem River. Various parts of the line operated until the 1940s and the 1980s. The main line of the railroad is now devoted to bicycle and pedestrian paths. They are the South County Trailway on the parts south of Route 119, and the North County Trailway north of 119.

To slake the thirst of its ever-growing population, which had reached almost 100,000 by 1915, Yonkers tapped the Saw Mill. Water from an impoundment two miles (3.2 km) north of downtown was held in two reservoirs and two water towers. It was purified by slow filtration through sand and then chlorinated. By 1919 the city was drawing an average of 10.6 million gallons (40,000 m³) a day from the river through this system.

Despite this, the pollution of the river continued unabated, reversing its earlier recovery. In a 1920 report on the condition of public water supplies around the state, New York's Health Department said "sanitary conditions upon the Saw Mill watershed are very unsatisfactory", despite the considerable rules and regulations it had promulgated to protect the river in Yonkers. The city's own public works department had noted dozens of violations for the previous year, most of them continued from the years before that. "A great many privies and cesspools are located on the edge of the Saw Mill and its tributaries and there is also drainage from poultry yards, barnyards and house drains," the department noted

Rather than enforce the violated regulations more strictly and clean up the river, the city chose to cover it up entirely. Between 1917 and 1922, the last 2,000 feet (610 m) of river, including a small gorge, was buried in a flume under the Getty Square neighborhood, an effort to halt the river's frequent floods and quarantine its unsanitary water, and open up some space for further development. That same decade, the county parks commission proposed to build the Saw Mill River Parkway along the river, just as the 1922 Bronx River Parkway follows the Bronx River, and to add a sewer line along the river to prevent contamination of Yonkers' water supply. Construction began in 1929 and continued throughout the Great Depression. By 1940, the parkway had reached the river's headwaters at Chappaqua, where World War II temporarily halted construction. In 1954, it was complete. The parkway's construction, along with that of the New York State Thruway later in the decade, required some adjustment of the river's course in some areas.

Westchester's postwar development led to more stormwater runoff, which often flooded and closed the parkway. By 1958, engineers were urging that the river be cleaned up to reduce flooding. Still, illegal dumping and overflows continued. For example, storm runoff gave the Yonkers section the river's highest concentrations of heavy metals, PCBs, and other chemicals, according to a study of the river in 1983, the year the city stopped using the Saw Mill as its primary water source. A decade later, the sediment in the Saw Mill had the highest concentration of metals in the United States Geological Survey's entire water-quality assessment program.

2000s

A new kind of pollution entered the lower Saw Mill in 2003 when a Yonkers sugar refinery spilled hydrochloric acid into the river. Westchester District Attorney Jeanine Pirro brought criminal environmental charges against American Sugar Refining, the plant owner, which was forced to pay a $20,000 fine; make a $100,000 donation to Riverkeeper, a regional environmental organization that focuses on the Hudson and its tributaries; and give one ton (800 kg) of sugar to Westchester Food-PATCH, a local nonprofit that supplies food to other nonprofits. Riverkeeper passed the money it received along to the Saw Mill River Coalition for local projects in Yonkers.

In 2008, Groundwork Hudson Valley, the coordinator of the Saw Mill River Coalition, received a three-year, $889,183 U.S. Environmental Protection Agency Targeted Watershed Grant. One of 15 recipients from a nationwide pool of more than 100 applicants, the group cleans up garbage, removes invasive species, and plants native trees along the river. The group also marks storm drains that drain to the river. On September 25–26, 2009, the Saw Mill River Coalition organized a BioBlitz to catalog species of plant life, animal life, insects, fungi, and bacteria in the river and its watershed. The Coalition is also looking to restore the wetlands along the river in order to reduce flooding.

Raising of the Saw Mill Parkway continues; in 2013, a 900-foot (270 m) stretch in Pleasantville was raised by three inches to reduce flooding from the river.

Daylighting

2011 daylighting construction

In 2007, the City of Yonkers and its partner agencies, which included Groundwork Hudson Valley and Creative Habitat, began planning a $34 million effort to expose parts of the flume to daylight. The project, which is part of the city's $3 billion redevelopment plan, aims to expose about six blocks of the river by 2015.

The first phase of the project removed a parking lot that covered a two-block section of the river in the Getty Square neighborhood of downtown Yonkers. Ground was broken on December 15, 2010, and the work was completed in December 2011. Work on the second phase, which aims to expose the river in the Mill Street Courtyard, began on March 19, 2014.

The project has stimulated real estate investment in the area.

Hydrology

The USGS maintains a stream gauge on the Saw Mill just above the river's mouth in Yonkers. Mean discharge since 1944 has been 32 cubic feet (0.91 m³) per second, with extremes of 1,840 cubic feet (52 m³) during the April 2007 nor'easter and 0.11 cubic feet (3,100 cm³). Average annual precipitation in the watershed is 46.2 inches (1,170 mm).

Saw Mill River Sewer Marker

The river's water quality varies, reflecting its history and surroundings. Its headwaters in the town of New Castle are considered "relatively healthy". There the river is less disturbed, and its ecosystem supports a diversity of organisms. In Yonkers, where it flows through a concrete-lined channel, there is less life in the water and it is considered to be environmentally impaired. A 1983 U.S. Geological Survey (USGS) study found that concentrations of heavy metals in the water increased further downstream, a phenomenon observed with many other pollutants in the river and correlated with the urbanization around and above its mouth. DDT was detected in the streambed sediments throughout the river. In its final 6 miles (9.7 km), more than 50 micrograms of PCBs were found per kilogram of water. In the 1990s, the USGS found that of the 35 Hudson tributaries it tested, the Saw Mill had the worst levels of cadmium, copper, mercury, nickel and zinc in the sediments near its mouth, and among the worst nationwide (however, only the river's manganese levels were found to exceed federal standards). It is believed to add more pollution to the Hudson than any other single tributary.

Unusually for a river, the Saw Mill's waters have consistently demonstrated a slightly alkaline pH, suggesting it has not been as affected by acid rain as other Hudson tributaries. In 1951, a state Department of Health survey reported pH between 7.25 and 9.1. Four decades later, another study found pH readings rising steadily from 7.59 in Chappaqua to 8.24 in Yonkers. Rising alkalinity as the river flowed toward Yonkers was also reported by a 2007 Manhattan College study done for the New York State Water Resources Institute that monitored the river for a year. It found a median low of 7.36 in Chappaqua and a median high of 7.81 near Torre Road in Yonkers, with a drop to 7.67 at the tunnel, for a total median for the river of 7.59. The lowest recorded pH was 7.1 at Chappaqua with the highest reading, 8.17, at Torre Road. All results were within the 6.5–8.5 range required by state regulations.

The 1983 USGS study also classified the water quality of the entire river. The first 14.5 miles (23.3 km) from the river's source in Chappaqua was classified as suitable for any purpose besides drinking. The next 6.0 miles (9.7 km) was classified as being safe to drink. The last 3.0 miles (4.8 km) of the river from the sewage treatment plant to the Hudson was determined to be unsafe to drink, bathe in or fish in. The water was only safe for agricultural and industrial use.

Saw Mill River Parkway flooded after Hurricane Irene

In regulations adopted in 1985 and amended in 2008, New York's Department of Environmental Conservation (DEC) divides the river into four water-quality regions similar to those in the 1983 USGS study. The first 1,100 feet (340 m) from the Saw Mill's mouth is affected by the Hudson's tides and thus is often salty like the river at that point. It is considered Saline Class B surface water, to be kept suitable for primary and secondary contact recreation such as swimming, boating and fishing, and capable of supporting "fish, shellfish and wildlife propagation and survival." The next section extends to the tailwater at the Yonkers sewage plant impoundment, and is Class C fresh water, with the same purposes, to the extent that "other factors" do not limit them. From there to the Woodlands Lake inlet is the third section, designated as Class A fresh water, to be kept clean enough for drinking. The remainder to the source is the fourth section, designated Class B, or fresh water kept to the same standards as the salt water above the river's mouth. Tributaries, named and unnamed, and subtributaries are generally held to the same standards as the section into which they drain.

A 1991 study by Irene Gruenfeld, a Williams College undergraduate, measured various pollutants at eight points along the river, from just below the duck pond in Chappaqua to inside the tunnel in Yonkers. The levels increased as the river flowed along, suggesting that most pollutants, especially dissolved salts, came from urban runoff instead of any single point source. The exception was PCBs, which rose drastically south of Elmsford (a finding that concurred with an earlier study) and then doubled in Yonkers. The study noted that this suggested a point source, perhaps a known burial site for used capacitors in the Elmsford area, yet Gruenfeld argued that cleaning up this and other possible point sources would not eliminate PCBs in the river. While the PCBs in the river were found somewhat biodegraded, chlordane levels are high enough that DEC recommends eating no more than a half-pound (230 g) of fish or eel from the Saw Mill per month.

A 2004-05 EPA study of the river rated the water quality 6 out of 100. The study also discovered that dissolved oxygen levels in the water were low because there were few organisms, poor sediment, and little plant life in the river. Although storm water from residential neighborhoods added dissolved oxygen, it also brought ammonia from fertilizer. The Army Corps of Engineers found that the channeling prevented aquatic life from sustaining itself; few fish naturally spawn in the river because of the cement casing and flume at its mouth.

Two years later, a joint study by Manhattan College and the New York State Water Resources Institute found high levels of human fecal bacteria in the water, likely due to municipal wastewater. All 12 sites exceeded the state maximum of a monthly median of 200 organisms per 100 milliliters (ml) over five months. Levels were, as with most of the river's other pollutants, generally highest near the mouth. However, the uppermost sampling site in the study, at the Chappaqua Metro-North station recorded the greatest single reading of any site, 1.2 × 10⁵ organisms per 100 ml, as well as the second highest; the researchers speculated that this was due to sewer overflow in the area at the times of those readings. Most high coliform readings were associated with significant rainfall events except at the two sites furthest downstream; the study theorized that some older buildings in this area of Yonkers may still discharge sewage directly to the river. Since most of the river flows under the shade of a forest canopy, the bacteria may be less likely to be inactivated by sunlight than in other streams.

Visual pollution is also an issue. The riverbanks in Yonkers are often lined with tires, shopping carts, plastic bottles, and other types of trash. In 2008, DEC's own inventory of the state's water resources reported that the river from the mouth to the end of the tunnel remained impaired and aesthetically stressed. "Urban refuse (tires, bottles, cans, etc.) lines much of the lower river," it reported. "Oil/gasoline slicks are regularly observed along this segment."

The stretches further upriver were slightly better. Between the end of the tunnel and Woodlands Lake, the river was still found to be impaired for recreation, drinking and aquatic life purposes, but not aesthetically, and as a whole the habitat was merely stressed. Above that point, the Saw Mill's waters were merely stressed for aquatic life and recreation, with only fish consumption considered to be impaired. DEC did not know the sources of pollutants in this stretch and called for further research."

Geology

The Saw Mill's basin is part of the Manhattan Hills in the New England Uplands physiographic region. It is primarily underlain by metamorphic rock such as gneiss, schist and marble. They can be seen in some bedrock outcrops in and around the river.

Soils in the river and its basin reflect past glaciation in the area. Glacial till covers much of the river bottom in its headwaters. Further downstream there is stratified drift and alluvium in the sediments.

Flora and fauna

Juvenile American eels

The American eel lives in the river. The eels commonly are born in the Atlantic Ocean and then swim through rivers and into tributaries. The eels inhabiting the Saw Mill River maneuver through the river's tunnel under Yonkers before reaching the more natural parts of the river farther upstream. The eels also scale a 20-foot (6.1 m) dam before reaching Woodlands Lake. These eels grow up to 5 feet (1.5 m) in length while living upstream. Later on, the eels swim back downstream into the Hudson and back into the ocean in order to reproduce. The planned installation of a netting system along the daylighted portion of the river (meant to prevent trash from flowing into the Hudson) would also prevent the eels from leaving the river to reproduce.

The Saw Mill was also known as the closest trout-fishing river to New York City. In the early 2000s, it was stocked with a few hundred trout each year.

Numerous deer live along the river and the parkway. These deer can be destructive to the ecosystem surrounding the river because they destroy low-lying plants, shrubs, and tree saplings, eliminating the food supply for smaller animals. About ten to 20 deer per square mile (26 to 52 deer per square kilometer), which is above the carrying capacity of the surrounding ecosystem. Deer also cause numerous accidents along the parkway. Car-deer encounters in Hastings average about 1.6 encounters per month.

See also

• List of rivers of New York

External links

• Report on daylighting the Saw Mill River by the US Environmental Protection Agency
• Course of the river on OpenStreetMap
• Saw Mill River Coalition's history of the river
• Groundwork Hudson Valley